Date Awarded

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Abstract

Validation of daily increment deposition in otoliths of juvenile striped bass up to 80 days of age was provided through sequential sacrifice of known age hatchery-reared fish in 1987 and 1989, and through tetracycline marking of otoliths of cage-cultured striped bass in 1989. Ages of fish between 80-110 days old were consistently underestimated by 1-3 growth increments. Known age juvenile striped bass were raised in the laboratory in 1989 under controlled environmental conditions. These experiments provided evidence of an endogenous circadian rhythm controlling daily increment deposition in juvenile striped bass otoliths. Juvenile striped bass were collected in the 4 Virginia river systems in 1986 and 1987. A total of 542 otoliths were aged using daily growth increments. Comparisons of back-calculated birthdate distributions between populations showed consistency between rivers within years, but not between years. Variations in cohort growth rates appeared to be related to the relative cohort size of fish surviving to the juvenile stage. A comparison of mortality for 14-day cohorts showed no trends between early and late hatched fish, and no relationship was found mortality and average growth rates for these cohorts. Population growth rates for the period June-September were linearly modelled, and ranged from 0.301-0.597 mm/day and 0.027-0.124 g/day. Mortality estimates for 60-90 day old striped bass ranged from 1.88-3.98% loss/day. Catch-per-unit-effort, as measured as the number of fish per seine haul, ranged from 4.0-29.6. Growth rates in both length and weight were positively correlated with condition factor and stomach fullness, suggesting food availability may play an important role in regulating juvenile striped bass growth. There was no apparent relationship between growth and CPUE. The relationships between growth and mortality, and mortality and CPUE, are ambiguous, and more estimates are needed to determine whether a density-dependent effect is controlling year-class strength and recruitment into the juvenile stage.

DOI

https://dx.doi.org/doi:10.25773/v5-nbm9-3912

Rights

© The Author

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